Calorie restriction may help mice stay slim: study

Calorie restriction may help mice stay slim and live longer, but it also means thicker fur for the animals, a new study said Tuesday.

Calorie restriction may help mice stay slim and live longer, but it also means thicker fur for the animals, a new study said Tuesday.

Researchers in Brazil reported in the U.S. journal Cell Reports that mice may use this as an evolutionary adaptation to stay warm and alive in limited food conditions.

"The changes in the fur and skin were quite noticeable, and are interesting because they were visible after only a few months, when animals are not yet old," said senior author Alicia Kowaltowski, a professor at the University of Sao Paulo's Institute of Chemistry.

"The changes may be related to an increase in skin stem cells, which help preserve the skin from the effects of aging, which we were also able to detect."

A calorie-restricted diet has already been associated with a long list of health benefits, from increasing lifespan and reducing insulin resistance to helping to fight cancer.

In the new study, the researchers compared mice that could eat everything they wanted, at any time -- which meant they eventually became overweight -- with animals restricted to eat 60 percent of the calories of what their more indulgent counterparts were allowed for six months.

The calorie-restricted mice lost around half of their body mass, but displayed more even, thicker, and longer fur coats.

At the cellular level, the group observed an expansion of hair follicle stem cells leading to increasing hair follicle growth and retention rates.

Compared to the free-ranging mice, the calorie-restricted mice also had three times as many blood vessels in their skin, to bring more warm blood to the surface, and their skin cells exhibited differences in metabolism so that they lost less energy as heat over time.

The researchers then shaved patches of fur off of mice from both groups to confirm that the extra hair helps warm the calorie-restricted animals.

"Indeed, based on heat loss measurements, the thicker fur coats helped insulate heat, and without the adaption, the calorie restricted mice were more lethargic and showed signs of disrupted metabolism," they said in a statement.

Kowaltowski said that if we understand these pathways involved in promoting the changes in skin related to calorie restriction, we could uncover targets to keep the skin healthy during aging.